Clostridium difficile and its toxin are central to the pathogenesis of antibiotic-associated diarrhea 1 disease (AAD). the laboratory diagnosis of AAD has depended on the demonstration of C. difficile toxin in fecal filtrates by a cell culture assay. Due to a lack of cell culture capabilities in many clinical laboratories, his study is to evaluate the usefulness of counter-immunoelectrophoresis (CIE) as a screening test for C. difficile toxin assay.